JPH09324476A - Manufacture of ceramic sound absorbing material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method having the capability of eliminating the need of forming an air layer behind, or being combined with other materials, and maintaining an optimum sound absorbing characteristic, particularly under the control of the sound absorbing characteristic of a frequency lower than a sound absorbing peak frequency, depending on an application field or a noise at an installation place. SOLUTION: This sound absorbing material is made of a ceramic block having main pores of diameter between 0.2 and 2,000μm for communication, permeability equal to or above 1cm<3> .am/cm<2> .sec.cm H2 O, and porosity equal to or more than 60%. In this case, many non-through holes are drilled in one side of the sound absorbing material orthogonal with the thicknesswise direction thereof, and the back thickness of the non-through holes is changed, thereby changing acoustic absorptivity at a frequency lower than a sound absorbing peak frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention properly controls the sound absorbing characteristics of a ceramic sound absorbing material having excellent weather resistance, particularly the sound absorbing coefficient at a frequency lower than the sound absorbing peak frequency, according to the use and the noise of the installation site. The present invention relates to a method for manufacturing a ceramic sound absorbing material.

[0002]

2. Description of the Related Art Conventionally, as a sound absorbing material, mineral fiber based sound absorbing materials such as glass wool and rock wool have been typical. However, the mineral fiber-based sound absorbing material has the drawbacks that when it contains water, the sound absorbing performance is significantly deteriorated, and because it is made of fibers, it deforms over time and is easily scattered or peeled off by a high-speed air flow.

[0003] Also, a sound absorbing material provided with a large number of through holes in a gypsum board is well known. The sound-absorbing material made of the perforated gypsum board absorbs sound energy by resonance in the through-hole, but has a drawback that it can only absorb a specific frequency. In order to solve this drawback, an air layer is provided in the back and a backing material such as glass wool is attached to the back, but these methods have a problem that the construction is troublesome.

Recently, ceramic and cement-based sound absorbing materials have been developed as sound absorbing materials which have excellent weather resistance, can be used outdoors, and are nonflammable and have a heat insulating effect. For example, a ceramic sound absorbing material is a material obtained by molding a ceramic material and firing it at a high temperature, and since it is porous, it has an action of absorbing sound energy by its fine pores.

[0005]

The above-mentioned conventional porous ceramics sound absorbing material has different sound absorbing performances depending on the degree of voids formed by pores, but the sound absorbing peak frequency is almost specified by the material, and the sound absorbing frequency There was a drawback that the area was small.

Therefore, an air layer is provided at the back, or, as disclosed in Japanese Patent Laid-Open No. 3-25108,
Attempts have been made to overcome the above-mentioned disadvantages by combining a porous ceramics sound absorbing material with an air layer and another porous material. However, these methods have drawbacks in that construction is time-consuming and costs are increased.

The present invention has been made in view of such conventional circumstances.
A ceramic sound-absorbing material with weather resistance that does not require an air layer behind it or is combined with other materials, and that has optimum sound-absorbing characteristics according to the application and noise at the installation site, especially the sound-absorbing characteristics on the low frequency side. An object of the present invention is to provide a method for manufacturing a sound absorbing material.

[0008]

In order to achieve the above object, the present invention has a continuous pore having a pore size of 0.2 to 2000 μm as a main component and an air permeability of 1 cm ³ · cm / cm ² · sec.
In a sound absorbing material composed of a ceramic block having cmH ₂ O or more and a porosity of 60% or more, a large number of non-through holes having a constant depth are formed on one surface perpendicular to the thickness direction of the sound absorbing material. The present invention provides a method for manufacturing a ceramics sound absorbing material, characterized in that the sound absorption characteristics on the lower frequency side than the sound absorption peak frequency are changed by changing the back thickness of the sound absorbing material.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The ceramic block which is the object of the present invention is a porous ceramic block having continuous pores, and is a pore-imparting material such as fire-resistant clay and / or fire-resistant chamotte in the form of spheres of expanded polystyrene or wood chips. , A fire-resistant heat-insulating brick made by mixing an inorganic binder such as water glass or feldspar, if desired, and molding, and then firing at a high temperature of about 1200 to 1700 ° C., and a similar structure Is. This ceramic block is
The main pore size is porous with continuous pores of 0.2 to 2000 μm.

The air permeability of this porous ceramic block can be changed depending on the type and particle size of the pore-imparting material and the firing conditions, but in order to obtain the desired sound absorbing effect, it is at least 1 cm ³ · cm / cm ² ·. An air permeability of sec · cmH ₂ O is required. The higher the air permeability is, the more excellent the sound absorbing effect is, but the air permeability of the ceramic block obtained by the above method is about 20 cm ³ · cm / cm ² · sec · cmH ₂ O as an upper limit. In the ceramic block obtained by the above method, when the porosity is less than 60%, the air permeability is reduced to 1 cm ³ · c.
m / cm ² · sec · cm H ₂ O or more is difficult,
If it exceeds 90%, the strength required for handling and processing cannot be obtained.

In the present invention, a large number of non-penetrating holes are formed in the ceramic block substantially regularly. The diameter of the non-through hole is preferably in the range of 2 to 15 mm. If this diameter is small, the number of non-through holes for obtaining the desired aperture ratio is large, and conversely, if the diameter is large, damage during drilling is likely to occur. Therefore, the range of 8 to 12 mm is more preferable. Further, a desired sound absorbing effect can be obtained if the aperture ratio of the non-through holes is in the range of 5 to 30%, but the range of 10 to 20% is preferable in order to obtain a more efficient and high sound absorbing effect. Although the sound absorption peak frequency changes by changing the depth of the non-through hole, the sound absorption peak frequency of the sound absorbing material hardly changes as long as the depth of the non-through hole is selected and made constant.

Further, it has been found that the sound absorption characteristics on the lower frequency side than the sound absorption peak frequency can be changed by changing the back thickness of the non-through holes provided in the ceramic block. In the present invention, the back thickness means the thickness from the bottom of the non-through hole to the surface on the opposite side of the ceramic block. The larger the back thickness, the more the sound absorption coefficient on the lower frequency side than the sound absorption peak frequency of the sound absorbing material can be improved, but in the range of the air permeability of 1 to 20 cm ³ · cm / cm ² · sec · cmH ₂ O. There is an optimum value for the back thickness. For example, ventilation rate 1-7
30 to 50 m for cm ³ · cm / cm ² · sec · cmH ₂ O
m, ventilation rate 7 to 14 cm ³ · cm / cm ² · sec · cmH ₂
O is 50 to 80 mm, and ventilation rate is 14 to 20 cm ³ · c
With m / cm ² · sec · cmH ₂ O, the improvement in sound absorption on the low frequency side is the highest with a back thickness in the range of 80 to 120 mm,
If the thickness exceeds this, the improvement effect will be reduced.

Therefore, when a non-through hole having a constant depth corresponding to a desired sound absorption peak frequency is provided, the back thickness of the non-through hole can be adjusted by changing the thickness of the ceramic block to be used. It is possible to obtain a ceramics sound absorbing material that has an optimum sound absorption peak frequency according to the application and the installation location and is capable of effectively absorbing low frequency noise. Particularly, the sound absorbing material having the depth of the non-through holes less than 70%, preferably 30 to 60% of the thickness of the ceramic block by adjusting the optimal back thickness in the above range of air permeability has a small total thickness. While suppressing, a large improvement in sound absorption effect can be obtained in the low frequency range.

According to the present invention, 200 to 2000
Shows good sound absorption performance in the HZ frequency range, and has a sound absorption peak frequency in the frequency range of approximately 300 to 1100 Hz. A level that can satisfy the sound absorption performance on the lower frequency side in accordance with any sound absorption peak frequency. Therefore, it is possible to manufacture a ceramics sound absorbing material which is excellent in weather resistance, high-speed airflow resistance and durability, and at the same time is effective for noise on the low frequency side.

The sound absorption coefficient according to the present invention is determined by JIS A
This was measured by a method of measuring a normal incidence sound absorption coefficient of a building material by a 1405 in-pipe method. The permeability of the ceramic block was measured in accordance with JIS R 2115,
The values are not multiplied by the kinematic viscosity of air.

[0016]

Example 1 As a ceramics block, a fire-resistant clay and a fire-resistant chamotte were mixed with wood chips as a porosity-imparting material, which was molded and then fired at 1300 ° C. to obtain a pore diameter of 0.2 to 200.
It has 0μm communication holes, has a bulk specific gravity of 0.8 and an air permeability of 4.
A refractory insulating brick of 2 cm ³ · cm / cm ² · sec · cmH ₂ O was used. A large number of non-penetrating holes each having a depth of 30 mm and a hole diameter of 8 mm were bored at a hole pitch of 22 mm on one surface of the refractory insulating bricks having different thicknesses, and the back thicknesses of the non-penetrating portions were 10, 20, 30, 40, respectively. Six types of ceramic sound absorbing materials having different sizes of 50 and 70 mm were manufactured.

The sound absorption coefficient of each of the obtained ceramic sound absorbing materials was measured, and the obtained sound absorbing characteristics are shown in FIG. As can be seen from these results, by changing the back thickness (changing the thickness of the sound absorbing material) while keeping the depth of the non-through holes constant, the sound absorbing peak frequency becomes approximately 1020 Hz, and the sound absorbing peak increases as the back thickness increases. Lower than the frequency, mainly 600Hz
It was possible to improve and improve the sound absorption coefficient in the lower frequency range.

Example 2 The same number of non-penetrating holes as in Example 1 except that the depth was 50 mm was formed in each of the refractory insulating bricks which were the same as in Example 1 but differed only in the thickness, and each non-penetrating hole. The thickness of the hole is 10,
Five types of ceramic sound absorbing materials having different sizes of 20, 30, 40, and 50 mm were manufactured.

The sound absorption coefficient of each of the obtained ceramic sound absorbing materials was measured, and the obtained sound absorbing characteristics are shown in FIG. As in Example 1, by increasing the back thickness of the non-through holes, the sound absorption coefficient at a sound absorption peak frequency of approximately 620 Hz, which is lower than the sound absorption peak frequency, mainly in the frequency range lower than 400 Hz, is improved. I was able to do it.

Example 3 A plurality of non-through holes each having a depth of 50 mm and a hole diameter of 8 mm were drilled at a hole pitch of 16 mm in each of the refractory heat insulating bricks having the same thickness as that of the above-mentioned Example 1 but having a different thickness. 1 back
Four types of ceramics sound absorbing materials were manufactured with different thicknesses of 0, 20, 30, and 50 mm.

The sound absorption coefficient of each of the obtained ceramic sound absorbing materials was measured, and the obtained sound absorbing characteristics are shown in FIG. As can be seen from these results, at a sound absorption peak frequency of approximately 620 Hz, the thicker the back thickness, the better the sound absorption coefficient in the frequency range lower than the sound absorption peak frequency, mainly in the frequency range lower than 600 Hz.

Example 4 In the same manner as in Example 3 except that the hole pitch of the non-penetrating holes was set to 30 mm, the refractory insulating bricks having different thicknesses were punched, and the back thickness of each non-penetrating hole was 10, 20, 30, 5
Four types of ceramics sound absorbing materials having different thicknesses of 0 mm were manufactured.

The sound absorption coefficient of each of the obtained ceramic sound absorbing materials was measured, and the obtained sound absorbing characteristics are shown in FIG. By increasing the back thickness of the non-through hole, it is almost 300-400H.
With the sound absorption peak frequency of z, it was possible to improve and improve the sound absorption coefficient in the frequency range lower than the sound absorption peak frequency, mainly in the frequency range lower than 200 Hz.

Example 5 A ceramic block having a pore size of 0.2 to 2000
It has a communication hole of μm, a bulk specific gravity of 0.45 and an air permeability of 6.
A refractory insulating brick of 0 cm ³ · cm / cm ² · sec · cmH ₂ O was used. A large number of non-penetrating holes each having a depth of 30 mm and a hole diameter of 8 mm are bored at a hole pitch of 22 mm on one surface of each refractory insulating brick having different thicknesses, and the back thicknesses of the non-penetrating portions are 10, 20, 30, 40, respectively. , 50 mm, and 5 types of ceramic sound absorbing materials were manufactured.

The sound absorption coefficient of each of the obtained ceramic sound absorbing materials was measured, and the obtained sound absorbing characteristics are shown in FIG. By increasing the thickness of the non-through holes, the sound absorption peak frequency is approximately 800 Hz, which is lower than the sound absorption peak frequency.
The sound absorption coefficient mainly in the frequency range lower than 500 Hz could be improved and improved.

Example 6 The same large number of non-penetrating holes as in example 5 except that the depth was 50 mm was formed in each refractory insulating brick similar to the above-mentioned example 5 except for the thickness. Each has a back thickness of 10,
Five types of ceramic sound absorbing materials having different sizes of 20, 30, 40, and 50 mm were manufactured.

The sound absorption coefficient of each of the obtained ceramic sound absorbing materials was measured, and the obtained sound absorbing characteristics are shown in FIG. By increasing the thickness of the non-penetrating holes, it was possible to improve and improve the sound absorption coefficient at a sound absorption peak frequency of about 500 Hz and on a lower frequency side than the sound absorption peak frequency, mainly in a frequency range lower than 400 Hz.

Example 7 A ceramic block having a pore diameter of 0.2 to 2000
It has a communication hole of μm, a bulk density of 0.32, and an air permeability of 2
A refractory insulating brick of 0 cm ³ · cm / cm ² · sec · cmH ₂ O was used. A large number of non-through holes each having a depth of 30 mm and a hole diameter of 8 mm are bored at a hole pitch of 22 mm on one surface of each refractory heat insulating brick having different thicknesses, and the back thicknesses of the non-through portions are 10, 20, 30, 40, respectively. , 50 mm, and 5 types of ceramic sound absorbing materials were manufactured.

The sound absorption coefficient of each of the obtained ceramic sound absorbing materials was measured, and the obtained sound absorbing characteristics are shown in FIG. By increasing the back thickness of the non-through hole, it is almost 500-1000.
With the sound absorption peak frequency of Hz, it was possible to improve and improve the sound absorption coefficient in the frequency range lower than the sound absorption peak frequency, mainly in the frequency range lower than 800 Hz.

Comparative Example A ceramic block having a pore size of 0.2 to 2000
Has communication holes of μm, bulk specific gravity of 1.1, and air permeability of 1.3
A refractory insulating brick of cm ³ · cm / cm ² · sec · cmH ₂ O was used. A large number of non-penetrating holes each having a depth of 30 mm and a hole diameter of 8 mm were bored at a hole pitch of 22 mm on one surface of each refractory insulating brick having different thicknesses, and the back thicknesses of the non-penetrating parts were changed to 10, 20, and 30 mm, respectively. Three types of ceramic sound absorbing materials were manufactured.

The sound absorption coefficient of each of the obtained ceramic sound absorbing materials was measured, and the obtained sound absorbing characteristics are shown in FIG. From this result, it was not possible to change the sound absorption coefficient in the low frequency range by forming a non-through hole in the ceramic block having a bulk specific gravity of more than 1.0 and changing its back thickness.

[0032]

EFFECTS OF THE INVENTION According to the present invention, it is not necessary to provide an air layer behind or combine with other materials, and the sound absorbing characteristics of ceramic sound absorbing materials, particularly the sound absorbing coefficient in the frequency region lower than the sound absorbing peak frequency, can be used in applications and It can be changed according to the noise of the installation site.

Therefore, it has excellent weather resistance, high-speed airflow resistance and durability as well as soundproofing for factories, various plants and equipment, and for soundproofing outdoors such as roads and railways. It is possible to manufacture a ceramics sound absorbing material having optimum sound absorbing characteristics according to noise.

[Brief description of drawings]

FIG. 1 is a graph showing the sound absorption coefficient of each ceramic sound absorbing material of Example 1 in which the back thickness of a non-through hole is changed.

FIG. 2 is a graph showing the sound absorption coefficient of each ceramic sound absorbing material of Example 2 in which the back thickness of the non-through holes is changed.

FIG. 3 is a graph showing the sound absorption coefficient of each ceramics sound absorbing material of Example 3 in which the back thickness of the non-through holes is changed.

FIG. 4 is a graph showing the sound absorption coefficient of each ceramic sound absorbing material of Example 4 in which the back thickness of the non-through holes is changed.

FIG. 5 is a graph showing the sound absorption coefficient of each ceramic sound absorbing material of Example 5 in which the back thickness of the non-through holes is changed.

FIG. 6 is a graph showing the sound absorption coefficient of each ceramics sound absorbing material of Example 6 in which the back thickness of the non-through holes is changed.

FIG. 7 is a graph showing the sound absorption coefficient of each ceramics sound absorbing material of Example 7 in which the back thickness of the non-through holes is changed.

FIG. 8 is a graph showing the sound absorption coefficient of each ceramic sound absorbing material in which the back thickness of the non-through hole of the comparative example is changed.

Claims (2)

[Claims] 1. The main pore size is 0.2 to 2000 μm, and the ventilation rate is 1 cm ³ · cm / cm ² · sec.
In a sound absorbing material composed of a ceramic block having cmH ₂ O or more and a porosity of 60% or more, a large number of non-through holes having a constant depth are formed on one surface perpendicular to the thickness direction of the sound absorbing material. A method for manufacturing a ceramics sound absorbing material, characterized in that the sound absorbing characteristics on the low frequency side of the sound absorbing peak frequency are changed by changing the back thickness of the sound absorbing material. 2. The method for producing a ceramic sound-absorbing material according to claim 1, wherein the ceramic block is obtained by firing refractory clay and / or refractory chamotte mixed with a pore-forming material. .